Tweet
Did yamaha make a 1996 90hp motor with low compression.
-
-
The older, carbed 2 stroke Yamahas had low(compared to 4 strokes) compression ratios. My 1999 90C has 5.76:1,5:67:1 and 5:86:1(each cylinder slightly different) compression ratios, but these ratios are figured differently than a 4 stroke motor...believe the 2 stokes are figured from the time the piston closes all the ports up to Top Dead Center, whereas 4 strokes are figured from bottom of stroke to the top. That's about all I know about it...maybe some of the real guru's on here can add something more!
-
This is a two stroke, i know a 2 stroke is lower than a 4 stroke. Let me say this diffent i just had my 90 rebuild i dont know what the compression was from the start but after the rebuild it is only a 105 across the board it should be alot more. But i herd that they made some motor that started with from the plant with low compression, did they is my question.Comment
-
105 in all 3 cylinders sounds great to me, especially if the rebuild included new rings and pistons and the motor hasn't been run enough to "seat" the new rings in the cylinders. All new or rebuilt motors would expect to have a lower compression before "break-in" period. Regarding compression Ratios, I'm not sure how low an engine can be made and still produce much power. Like I said, my 90C has about 5.75:1 average compression ratio, and that seems fairly low to me...it runs on 87 octane/regular gas.Comment
Comment